public void testPollFirst() {
    assertEquals(a, navigableMap.pollFirstEntry());
    assertEquals(entries.subList(1, entries.size()), copyToList(navigableMap.entrySet()));
  }

  @MapFeature.Require(absent = SUPPORTS_REMOVE)
  public void testPollFirstUnsupported() {
    assertThrows(UnsupportedOperationException.class, () -> navigableMap.pollFirstEntry());
  }

  @CollectionSize.Require(SEVERAL)

      assertTrue(Thread.holdsLock(mutex));
      return delegate().navigableKeySet();
    }

    @Override
    public @Nullable Entry<K, V> pollFirstEntry() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate().pollFirstEntry();
    }

    @Override
    public @Nullable Entry<K, V> pollLastEntry() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate().pollLastEntry();

  public void testPollFirst() {
    assertEquals(a, sortedMultiset.pollFirstEntry());
    assertEquals(asList(b, c), copyToList(sortedMultiset.entrySet()));
  }

  @CollectionFeature.Require(absent = SUPPORTS_REMOVE)
  public void testPollFirstUnsupported() {
    assertThrows(UnsupportedOperationException.class, () -> sortedMultiset.pollFirstEntry());
  }

  @CollectionSize.Require(SEVERAL)
  public void testLower() {

  public void testPollFirst() {
    assertEquals(a, sortedMultiset.pollFirstEntry());
    assertEquals(asList(b, c), copyToList(sortedMultiset.entrySet()));
  }

  @CollectionFeature.Require(absent = SUPPORTS_REMOVE)
  public void testPollFirstUnsupported() {
    assertThrows(UnsupportedOperationException.class, () -> sortedMultiset.pollFirstEntry());
  }

  @CollectionSize.Require(SEVERAL)
  public void testLower() {

    return delegate().firstEntry();
  }

  @Override
  @CheckForNull
  public Entry<E> lastEntry() {
    return delegate().lastEntry();
  }

  @Override
  @CheckForNull
  public Entry<E> pollFirstEntry() {
    throw new UnsupportedOperationException();
  }

  @Override
  @CheckForNull
  public Entry<E> pollLastEntry() {
    throw new UnsupportedOperationException();
  }

  @Override

    public Entry<E> firstEntry() {
      return standardFirstEntry();
    }

    @Override
    public Entry<E> lastEntry() {
      return standardLastEntry();
    }

    @Override
    public Entry<E> pollFirstEntry() {
      return standardPollFirstEntry();
    }

    @Override
    public Entry<E> pollLastEntry() {
      return standardPollLastEntry();
    }

    @Override

    public Entry<E> firstEntry() {
      return standardFirstEntry();
    }

    @Override
    public Entry<E> lastEntry() {
      return standardLastEntry();
    }

    @Override
    public Entry<E> pollFirstEntry() {
      return standardPollFirstEntry();
    }

    @Override
    public Entry<E> pollLastEntry() {
      return standardPollLastEntry();
    }

    @Override

    @Override
    public NavigableSet<K> navigableKeySet() {
      return fromMap().navigableKeySet();
    }

    @Override
    @CheckForNull
    public Entry<K, V2> pollFirstEntry() {
      return transformEntry(fromMap().pollFirstEntry());
    }

    @Override
    @CheckForNull
    public Entry<K, V2> pollLastEntry() {
      return transformEntry(fromMap().pollLastEntry());
    }

    @Override
    public NavigableSet<K> navigableKeySet() {
      return fromMap().navigableKeySet();
    }

    @Override
    @CheckForNull
    public Entry<K, V2> pollFirstEntry() {
      return transformEntry(fromMap().pollFirstEntry());
    }

    @Override
    @CheckForNull
    public Entry<K, V2> pollLastEntry() {
      return transformEntry(fromMap().pollLastEntry());
    }

        }
        return navigableKeySet;
      }
    }

    @Override
    @CheckForNull
    public Map.Entry<K, V> pollFirstEntry() {
      synchronized (mutex) {
        return nullableSynchronizedEntry(delegate().pollFirstEntry(), mutex);
      }
    }

    @Override
    @CheckForNull
    public Map.Entry<K, V> pollLastEntry() {
      synchronized (mutex) {